a. Field of the Invention
The present invention pertains generally to pressure testing of pipe and specifically to the pressure testing of polyethylene gas lines.
b. Description of the Background
Polyethylene (xe2x80x98Polyxe2x80x99) pipe has become popular for the construction of pipelines for various purposes. Poly pipe enjoys a low cost of installation and very efficient and quick joining technology in addition to being flexible and easy to install. Poly pipe is used for pressurized applications such as gas and water, and for unpressurized applications such as sewer.
In a natural gas distribution system for distributing gas to houses, a main line may be installed along a roadway initially and tees would be installed at a later date to complete the service from the main line to each house. The tee may be a saddle tap tee, such as shown in FIG. 1. The tee fitting 100 is sealed to the pipe 102 using multiple methods. After the tee 100 is sealed to the pipe 102, a cutting device located inside the tee 100 is engaged to penetrate the exterior surface of pipe 102 and allow communication of the fluid or gas inside the pipe 102 to flow through the tee 100. Such fittings are commonly used in the industry.
As stated above, a main line may be installed in the ground and feeder lines installed using tees to individual houses. A feeder line may be fully installed except for the penetration of the exterior of the main pipe when a pressurization test may be necessary to ensure proper installation.
In pressurized applications, especially with natural gas or propane, pressure testing of an installation or segment of an installation is mandatory before the segment can be put into service. Such a test requires that the segment of pipe be sealed off and pressurized with a gage applied. When the pressure source is removed, the segment of pipe must maintain pressure for a certain period of time to ensure that the pipeline has no leaks. After the test is successful, the exterior of the main line pipe may be penetrated through the tee fitting and the feeder line is thusly placed in service.
There are many different designs of tee fittings in commercial use. For example, the saddle tees may be fusion welded to the main line pipe or resistive heating may be employed between the fitting and the pipe to affect a weld. The sizes of main line pipe may range from two inch outer diameter to twelve, fourteen, or even larger sizes. The tee fittings are available in many different sizes, however, two sizes are most commonly used in feeder line applications. These sizes are one inch and two inch diameter.
Several different manufacturers supply these tee fittings. Each manufacturer may use a different sealing system and slightly different design. Some pressure test devices exist that attach to the tee fitting using the same threads and sealing system as the cap of the fitting. With the great number of different sealing systems, such as having an o-ring on the body of the fitting or located in the cap itself, and the use of specialized buttress threads in some fittings, a specialized pressure test adapter must be created for each manufacturer""s fitting design.
Alternative methods for performing a pressurization test is to install a special tee fitting along the course of the feeder line. The special fitting is installed solely for the purpose of performing the pressurization test and is not subsequently used once the feeder line is put into service. The disadvantage is that the additional test fitting is another potential leak path as well as being another expense.
It would therefore be advantageous to provide a device and method of testing a feeder line that would be applicable to many manufacturer""s tee fitting designs without having any changeover. It would be further advantageous if the apparatus and method did not require any additional fittings to be installed in the feeder line.
The present invention overcomes the disadvantages and limitations of the prior art by providing a device and method for sealing pressure test apparatus using the inside threaded portion of a tee fitting. Further, the device may be simply adapted from one size of tee fitting to a second size.
The present invention may therefore comprise a method for pressure testing a branch circuit of polyethylene pipe that is connected to a main line with a tapping tee fitting comprising: removing the cap of said tapping tee; adjusting the position of the hole cutter inside said tapping tee to a depth at least approximately equal to the diameter of said hole cutter; installing a pressure test adapter to said tapping tee, said adapter being adapted to engage the internal threads of said tapping tee, said internal threads being the threads in which said hole cutter is engaged, said adapter having an o-ring seal, said o-ring seal being adapted to seal against the surface of said tapping tee that is perpendicular to said internal threads, said adapter having a valve and a pressure gage; applying a pressure source to said valve to pressurize said tapping tee; indicating a pressure on said pressure gage; removing said pressure from said valve, said valve being engaged to hold said pressure inside of said tapping tee; and ensuring that said pressure is maintained within a predetermined limit for a predetermined time.
The present invention may further comprise a method for pressure testing at least two branch circuits of polyethylene pipe that is connected to a main line with at least two sizes of tapping tees comprising: removing the cap of a first tapping tee; adjusting the position of the hole cutter inside said first tapping tee to a depth at least approximately equal to the diameter of said hole cutter; installing a pressure test adapter to said first tapping tee, said adapter being adapted to engage the internal threads of said tapping tee, said internal threads being the threads in which said hole cutter is engaged, said adapter having an o-ring seal, said o-ring seal being adapted to seal against the surface of said first tapping tee that is perpendicular to said internal threads, said adapter having a valve and a pressure gage; applying a pressure source to said valve; indicating a pressure on said pressure gage; removing said pressure from said valve, said valve being engaged to hold said pressure inside of said first tapping tee; ensuring that said pressure is maintained within a predetermined limit for a predetermined time; selecting a second tapping tee for testing, said second tapping tee being a larger size than said first tapping tee; removing the cap of said second tapping tee; adjusting the position of the hole cutter inside said second tapping tee to a depth at least approximately equal to the diameter of said hole cutter; installing a size adapter into said second tapping tee, said size adapter having external threads adapted to engage the internal threads of said second tapping tee and internal threads adapted to engage the external threads of said pressure test adapter, said size adapter further having an o-ring seal adapted to seal against the surface of said second tapping tee that is perpendicular to said internal threads of said second tapping tee; installing said pressure test adapter to said size adapter such that said o-ring seal of said pressure test adapter engages said size adapter; applying a pressure source to said valve; indicating a pressure on said pressure gage; removing said pressure from said valve, said valve being engaged to hold said pressure inside of said second tapping tee; and ensuring that said pressure is maintained within a predetermined limit for a predetermined time.
The present invention may further comprise a pressurization test apparatus for performing a pressurization test on at least two tapping tees with internal threads of different sizes comprising: a pressurization test fitting having a valve adapted to receive pressurized air, a pressure gage adapted to indicate the pressure inside the pressurized circuit, and external threads adapted to fit inside the internal threads of a first tapping tee, said test fitting further comprising an o-ring seal adapted to seal against the surface perpendicular to said internal threads of said first tapping tee; and an size adapter having internal threads adapted to receive said external threads of said pressurization test fitting, a sealing surface perpendicular to said internal threads adapted to seal against said o-ring seal of said pressurization test fitting, external threads adapted to fit inside the internal threads of a second tapping tee, said second tapping tee being larger in size than said first tapping tee, said size adapter further having an o-ring seal adapted to seal against the surface perpendicular to said internal threads of said second tapping tee.
The advantages of the present invention are that several sizes of tapping tees may be pressure tested. Further, since the present invention will work with the tapping tees from many different manufacturers, custom test adapters for each manufacturer""s fittings are no longer required.